1. Field of the Invention
This invention relates to a hotmelt-adhesive fiber sheet and a process for producing the same. More particularly, it relates to a hotmelt-adhesive fiber sheet capable of being tightly adhered by heating on paper, clothes, timbers, metals, etc.
2. Description of the Related Art
Heretofore, as hotmelt-adhesive conjugate fibers or non-woven fabrics using the same, there have been known those obtained by subjecting polypropylene or polyester as a higher melting component and polyethylene or ethylene-vinyl acetate copolymer as a lower melting component, to conjugate spinning to obtain a web, followed by heat-treating the resulting web to fix the contact points of the fibers by melt-adhesion (see Japanese patent publication No. Sho 54-44773 and Japanese patent application laid-open No. Hei 2-49351).
However, while such conjugate fibers have a high adhesion with one another to give a non-woven fabric having a high tenacity, they have a low adhesion strength onto other materials such as paper, clothes, timbers, metals, etc., so that they have been insufficient as a raw material for composite materials. Further, there have been also known fibers using a copolymer of ethylene and an unsaturated carboxylic acid as a lower melting component of conjugate fibers, in order to improve the adhesion (see Japanese patent application laid-open No. Hei 1-92415), but such fibers have been also unsatisfactory.
As conjugate fibers having a high adhesion onto other materials, there have been known those obtained by blending a terpolymer of ethylene, acrylic acid ester and maleic anhydride into a lower melting component (see Japanese patent application laid-open No. Hei 3-133625, Japanese patent application laid-open No. Hei 3-287875 and Japanese patent application laid-open No. Hei 4-146300). In order to give a sufficient adhesion to these fibers, it is necessary to blend at least 15% by weight of such a terpolymer into a lower melting component.
However, terpolymers have a higher frictional force against metals and hence static electricity is liable to occur, resulting in an inferior spinnability so that fibers having a small fineness of 10 .mu.m or less is difficult to obtain. Thus, there have been raised many troubles such as winding of yarns around rollers at a drawing step or occurrence of naps at a carding step, etc. In order to overcome the above problems, it has been attempted to attach a surfactant to the fibers in a quantity as large as 0.15% by weight or more, but to the contrary, the adhesion of fibers has been lowered.